Reverberation unit magnetic assembly



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Aug. 30, 1966 J. VAN LEER REVERBERATION UNIT MAGNETIC ASSEMBLY FiledApril 26, 1962 Aug- 30, 1966 J. VAN LEER 3,270,300

REVERBERATION UNIT MAGNETIC ASSEMBLY Filed April 26, 1962 :5Sheets-Sheet a INVENTOR.'

Aug. 30, 1966 J. VAN LEER REVERBERATION UNIT MAGNETIC ASSEMBLY FiledApril 2G. 1962 5 Sheets-Sheet 5 .94 saw@ as INVENTOR.

United States Patent O 3 270 300 REVERBERATION UIT MAGNETIC ASSEMBLYJohan van Leer, Chicago, Ill., assigner to Hammond Organ Company,Chicago, Ill., a corporation of Delaware Filed Apr. 26, 1962, Ser. No.190,439 4 Claims. (Cl. S33-30) This invention relates in general toreverberation units for u-se with musical instruments, such as, ei-therorgans, radios or phonographs, and more par-ticularly relates to animproved and more economical magnetic arrangement for use in areverberation unit.

Reverberation units generally comprise several coil springs which serveas transmission lines to convey signals in different time intervals toan output circuit for the purpose of simulating the acoustical effect ofan auditorium. In such a unit there must be provided a signal generatingassembly or driver comprising an input coil at one end of the spring.The input coil responds to an input electrical signal for controlling atiny magnet attached to the adjacent end of the respective transmissionlines. This introduces a corresponding mechanical wave into thetransmission line which is sensed by a signal receiving assembly orpickup at the other end of the line. The pickup assembly comprisesanother magnet and coil which respond to the transmitted mechanical waveby providing an output electrical signal having a delayed intervaldependent on the length of the spring and the rate of wave transmission.This output signal is then applied through suitable amplifying devicesto an output transducer, such as a loud speaker, for the purpose ofsimulating the effect described above.

The reverberation unit utilizes at least two transmission lines foreifective operation. Each transmission line must have a small magnet a-tboth the driver and pickup ends and since signal values are minute,these must each be loca-ted in an area of maximum flux density generatedby ia coil at both the driver and pickup ends in order to functionefliciently. Thus the problems with respect to the signal generating andsignal receiving ends of the transmission lines revolve around the needto provide simple signal 4gener-ating and receiving apparatus which maybe duplicated at both ends and `for both lines since such an arrangementpermits the most economical construction and assembly and also providesthe maximum in magnetic ilux density from the available power.

In overcoming these problems the invention utilizes a coil and polepiece assembly of identical construction at both the driver and pickupends of the transmission lines. Each coil and pole piece assemblycomprises a simple interchangeable unlaminated two part pole piececonstruction having a left hand and right hand symmetry to permit anidentical magnetic circuit to be established for the magnets of therespective transmission lines. In addition, the po'le pieces eachincorpora-te a portion of the coil core structure, and each is assembledto the coil by inserting the core structure therein to simultaneouslyform the completed core. Thus the pole pieces are all interchangeablepermitting a simple standardization. In addition, the pole pieces areformed so that they are spaced in close proximity only over an areaadjacent the transmission line magnets. This prevents excessive fluxleakage and enables the flux to be confined to a prescribed area therebyincreasing its density and enabling the maximum eiliciency.

It is therefore an object of the present invention to p-rovi-de animproved driver and pickup assembly for a reverberation unit.

It is another object of the present invention to provide an improvedcoil and pole piece assembly for use in a reverberation unit.

Other objects together with the features of the present invention willbecome apparent on examination of the following speciiication, claimsland drawings, wherein:

FIG. 1 is an elevational view of the reverberation unit assembly;

FIG. la is an end view of the assembly shown in FIG. 1 with certaindetails omitted;

F-IG. 2 is a sectional view taken along the line 2--2 in FIG. l;

FIG. 3 is a sectional view taken along the line 3 3` in FIG. 2;

FIG. 4 is a sectional view taken along lthe line 4-4 in FIG. 3;

FI-G. 5 is a sectional view taken along the line 5-5 in FIG. 3;

FIG. 6 is a sectional view taken along the line 6 6 in FIG. 3;

FIG. 7 is an exploded perspective view of the magnet and pole pieceassembly; and

FIG. 8 is a sectional view illustrating the relationship between thecoil, pole pieces and magnets.

In the drawings, the reverberation unit assembly is indicated by thereference character 10. yIt comprises a channel member 12, a pair oftransmission l-ines 14 and 16, a driver unit assembly 18 and a pickupunit assembly 20. The channel member 12 comprises opposite longitudinalside Walls 22 and a back wall 23 therebetween. Each Wall 22 is providedwith apertures adjacent the pick- -up and driver assemblies forreceiving the ends of respective coiled springs 24e24c. The springs24-24c serve to suspend the reverberation unit 10 from a suit-ablemounting channel 25 for isola-ting the unit 10 from extraneousvibrations as explained in an application Serial No. 190,- 444 tiledApril 26, 1962 simultaneously herewith by William C. Laube, Jr.

T he driver and pickup units 18 and 20 are substantially identicallyconstructed and dimensioned. Each includes an integrally formed case 26having a pair of spaced apart depending L-shaped lugs 27 that extendthrough the back wall 23 as best seen in FIGS. 4 and 5 and projecttowards each other. A shoulder 28 on each lug limits the down- Wardmovement of the case. A leaf spring 30 is inserted between therespect-ive lugs 27 along the lower side of wall 23 to seat therespective cases 26 in position. An angle stop 32 on the leaf springengages the edge of wall 23y as best seen in FIGS. 2 and 3, while adetent 33 engages an aperture in wall 23 to control the position ofspring 30 and prevents its shifting. IIn addition, a ground strip 36 isinserted between the shoulder 28 and the top of wall 23 and is heldiirmly engaged the wall 23 when clip 30 is inserted.

Each case 26 comprises a generally rectangular main body 3-8 having sideaces 40, a front face 42, a back face 44, a top face 46, and a bottomface 48 from which the lugs 27 depend. A groove 50 in both the top andbottom faces extends back from the front face 42 towards the rear of thebody 38 and a sloping stop element 52 having a vertical rear wall 53 islocated in each groove as best seen in FIGS. 4 and 5.

The body 38 is provided with a deep substantially rectangular shapedrecess 54 in i-t-s yfront face 42. The recess 54 has side Awalls 515intersected by vertical stop walls 56. In the posterior portion of therecess 54 as seen in FIGS. 3 and 5, the vertical walls converge and anarrow aper- 4ture 58 connects the recess 54 to the back tace 44 of thebody. The .aperture 58 is adapted to receive a connector strip whichextends through the recess 54 for the purpose of enabling electricalconnections to be extended to a coil 62. The coil 62 comprises pant of acoil and pole piece assembly 64 adapted to be received in the recess 54and in a pair of horizontal slots 66.

A horizontal slot 66 connects each side of the recess 3 54 with the sidefaces 40 of the body 38 for a predeterdistaiice'froni' the front face42S Each slotm66 is i defined by hat upper and lower wall portions 68from the front face 42 to a position intermediate lthe slot ends andthen lby arcuate t-op and bottom wall portions 70 which terminate at -astop wall 72 as best seen in FIG. 6-. A narrow horizontal passageway 74connects each slot 66 .through thev Wall 72 to the back Iface 44 wherethe respective passageways terminate in a Jcircular opening 76 havingaligned narrow recesses 77 vcrosswise to .the slot 74 extending inwardlyfrom the opening 76.

The coil Yand pole piece 'assemblies `64 each comprise a bobbin 78 .onwhich the coil 62 is wound in a conventional manner. The bobbin 78 has arectangular passageway 80 therein and generally rectangular spool heads`82. A pair of pole pieces 84 are each adapted to be engaged on arespective spool head '82 and each has a core portion 86 for engagementin the passageway 80'.

v 'I'he pole pie-ces `84 each comprise an elongate web 88 of magneticmaterialand the respective core portions86 depend therefrom adjacent thetransverse axis of the web and to one side thereof. An Lshaped llange90` is provided a=t opposite ends of each pole piece .and eac-h flangehas an arm 92 extending in opposing directions. The core portions 86 are`inserted through spool heads 82 into opposite ends of passageway A80`and in abutting relationf ship. The webs 88 are thus supported so thatthe arms 92 on one` pole piece are in a more closely spaced relationshipto an arm on .the other pole piece than the pole piece webs. Thisreduces the -area of flux leakage to tha-tof arms 92 since only theseareas are in close proximity .to each other. The spacing betweenrespective arms 92 deiines the gaps 93 'of identical magnetic circuitsand atiny cylindrical magnet 94 at the end of each transmission line islocated in eac-h of .the gaps. The magnets 94 each have an axialdimension substantially the same .as the transverse ldimensionV of theassociated arms 92. It will be noted that .the magnet-s 94 i-ntersectIthe conlined main flux path in t-he limited area traversed by arms 92so that the maximum signal efficiency is achieved. In addition, theconstruction enables the gaps for the magnets a-t each end ofbothtransmission lines to be effectively defined by 'a single pair of polepieces and that these are'all interchangeable.' It will be noted thateach of the spool 'heads 82 is provided with a lboss 98 along one endand that a recess 100 is provided in one end of each boss. Each recess100 adapted to receive respective arms 102-.of the connector strip 60.The connector strip 60 is a llat elongate insulating plate 3 upon whichis ailixed a pairof thin conductive layers 1014 .to which respectiveleads 106 of the coi-l I wound to the same length with their turns incompressive relationship so that adjacent turns are normally touching.When assembled to the driver and pickup assemblies the springs arestretched to separate the lturns :and .the smaller diameter line 14 willof course transmit higher frequencies than the larger diameter line 16.However in the range where the frequency transmitted by line 16 beginsto fall off substantially, little acoustical effect is lost since inthat range the single line 14 contributes sutiicient reverbera- .tioneffect.

Due to the step in the tube 116 'a shoulder is formed which serves as astop for a flattened end of a support wire 1-24 inserted partiallytherethrough as best seen in FlG. 6. The support wire 124 is extended.through a rubber damping disc .126 an-d its other end is fastened along.one diameter of .an anchor disc 128 which serves as a bayonetconnection as will be explained. Thus, each transmission line 14 and 16is a self contained subassembly comprising a pair of coiled springs 1-20or 122 joined lin the center of the line and having at each end a magnet94, support wire 124, damping disc 126 and anchor disc 128.

To assemble the reverberation unit, la coil .and pole piece assembly 64is inserted in recess 54 i-n each case 26 with the tab 112 projectingfrom the rear Iof the case. The ground strip 36 which has an elongateleg 132 extending ltowards the front face 42 and lthis is bent over andinserted between the lower pole piece and associated spool head beforethe assembly 64 is inserted in recess 54. Each lare extended at lugs107. The strip has top yand botto-m stop portions 108 which .abut theback wall of recess 54 when the coil and pole piece assembly 64 isinserted in the recess 54. A tab portion on the connector strip extendsthrough aperture 58 for the purpose of extending external velectricalleads 112 to the coil. are positioned by a tab 1-14=tha t is st-akedonto wall 23.

The magnets 94 each have a central aperture in which a stepped tube 116is inserted and cemented thereto. The stepped tube 1.16 has a portion-Which is cemented to and crimped, about a respective straight end 118of a coil spring 120` or 122. The springs 120 and 122 each form a -par-tof a respective transmission line 14 or 1'6. Each transmissionlinecomprises two springs ,1.20 or 122 respective'ly joined, in t-hefcenter of .the line 'by anv eyelet, for example, an'dfconnected atopposite ends to the magnets 94. The springs 120 or 122 are joined sothat their windings are of opposite direction for .the purpose osuppressing undesired vibrational modes.

It will be noted lthat .although the springs of each transmission lineare of identical length 'that the springs 122 of the transmission line16 have a larger helix diameter than springs '120. `Thus the springs. ofeach line. are

The leads 112 :je

case' 26 is'mounted on the channel 12 and held thereto `by leaf spring30 either before or after the assembly 64 is 'assembled thereto, but ineither event the Walls 515 an-d 56 in recess 54 serve to control .theposition of the assembly 64.

The transmission lines 14 and 16 are assembled to the driver and pickupassemblies 18 and 20 by inserting the anchor disc 128 at one end of eachtransmission line through the passageway 74 and on passing therethroughandv being aligned with the circular opening 76, each is given a slightrotational movement and a slight pull thereon enables the anchor disc126 to be seated in the recesses 77 to form a bayonet connection. Sincethe anchor disc l128 is then no longer aligned with the passageway 74,

it cannot be pulled back through it so that one end of each transmissionline is held in position. The disc 128 at the other end of eachtransmission line is then inserted through a passageway 74 in either thedriver or pickup means as the case may be in the same fashion. f

The distance lbetween the two ends of passageways 74 is calculated tojust lstretch the springs so that their turns yare separated by anidentical amount with the turns having a low helix angle to insure theproper propagation of the transmitted waves while at the :same time thetotal spring length is held short. Thus, by the positioning of the cases26 the correct spacing between the turnsv can be easily achieved. Themagnets 94 then lie in the gaps 93 `formed between a respective pair ofarms 92 of the pole pieces.

v In order to properly position and secure the pole pieces with respectto the `magnets 94 while -securing the coil and pole piece assembly 64and in order to maintain the damping discs 126 properly positioned, aspring clip 134 is used to complete the positioning of the assembly. Theclip 134 is generally U-shaped with the ends ofthe side legs 135 havingring shaped slotted right angle arms 136 thereon. In addition, a pair ofwings 137 are provided at the end of each leg 135 and in the same plane,but projecting back therefrom at a transverse angle.

The vback leg 138 of the clip 134 is provided with respective upwardlyand downwardly projecting tines 139 and L-shaped arms 140. Each arm140has a locking bend 142 at the end thereof.

T-he clip 134 is assembled to the case 26 lby inserting the side legs135 together with wing 137 in the recess 54 'i while arms 140 engagegrooves 56. The slots in ring As the clip 134 is pressed back, the arms136 move the damping discs 126 through slots 66 between the arcuate Wallportions 70 and 72 to properly seat the same. At the Isame time thewings 137 press the Webs 84 of the pole pieces against the respectiveupper and lower walls yof recess 54 to size the gap 93 therebetween.Simultaneously the walls 56 serve as stops for the arms `90 so that thepole pieces are positioned properly with respect to the magnets 94.

The tines 139 serve to apply pressure against the coil and pole pieceassembly 64 and when the locking bend 140 on the clip passes Aover thevertical wall 53 of the stop 52, the assembly is securely held inposition.

A rectangular resilient shielding element 142 is slipped over the frontof the driver unit case 26 preferably before the transmission lines v14and 16 are assembled thereto. The element 142 has a set of ears 143which engage around a tab 144 protruding Ifrom the sides of each case sothat the element 142 is properly seated and supported. The element 142additionally seats the leg 132 of the ground strip 36 against the bottomface 48 ,of the case so that it is in no danger of entanglement.

There has been Idescribed one embodiment of my invention, and since thisembodiment is capable of many adaptations and modications, there isappended hereto a series of claims for accurately setting forth thelimitations of the invention.

I claim:

1. A spring type reverberation unit assembly comprising a base, a pairof spaced apart abutment units secured to said base, each Iof said unitsproviding a coil structure, core members for said coil structure, andsaid core members providing pole pieces with a magnetic gaptherebetween, a coil spring member, torsionally compliant mountingelements secured to the ends 'of said spring member and extending awayfrom said spring member substantially axially with respect to saidspring member, resilient damping members secured to said compliantelements, fittings secured to said compliant elements beyond saiddamping members, transversely permanently magnetized cylindricalelements secured substantially axially to the end of said :spring so asto rotate with the spring ends, mounting means on said units adapted forsecurement to said fittings to support said spring in stretchedcondition betewen said units with said magnetized cylindrical elementsWithin said magnetic gaps, means for securing said damping members tosaid units, and said fittings when secured to said units defining apredetermined angular relationship as between the polarity of saidmagnetized cylindrical elements and said pole pieces.

2. A coil and pole assembly for providing a pair of aligned spaced apartmagnetic gaps having substantially identical characteristics, comprisinga coil bobbin having parallel iiat ends and a rectangular core passagetherethrough between the ends, a coil Wound on said bobbin, a sheetmetal core strip extending into said passage from one end of said bobbinin face-to-face engagement with a second identical core strip extendinginto said passage from the opposite end of said bobbin, each of saidcore strips being bent over at right angles to provide a tab lyingagainst each end `face of said bobbin, each of said tabs beingintegrally edge joined to an offset transversely extending strip havingoffset L-shaped ends, the offset at both ends being in the `direction ofthe integral core strip, said offset ends forming pole pieces equallyspaced from the core passage, the L-shaped ends of one of saidtransverse strips being in alignment with the L-shaped ends of the otherof said transverse strips to provide a pair of magnetic gaps at eachside of said coil bobbin.

3. A pole piece structure, two of which used together provide a pair ofaligned spaced apart magnetic gaps having substantially identicalcharacteristics, comprising a narrow rectangular sheet metal core stripadapted to extend into a core passage of a coil, said core strip havingan integral tab at one end extending at right angles to the plane of thecore strip, said tab being integrally edge joined to an offsettransversely extending strip having offset ends, said transverse stripbeing tangential to said core strip, the offset at -both ends of thetransverse strip being in the direction of the integral core strip, said`offset ends 'forming pole pieces, and said pole pieces being equallyspaced from one `of the faces of the core strip.

4. A coil and pole assembly for providing a pair of aligned spaced apartmagnetic gaps having substantially identical magnetic characteristics,comprising a coil bobbin having parallel flat ends and a core passagetherethrough between the ends, a sheet metal core strip extending intosaid passage from one end of said bobbin in faceto-face engagement witha second identical core strip extending into said passage from theopposite end of said bobbin, each of said core strips 'being formedintegrally with a tangentially offset transversely extending striphaving offset ends, said offset ends forming pole pieces equally spacedlfrom the core passage, the `offset ends of one of said transversestrips being in alignment with the offset ends of the other of saidtransverse strips to provide a magnetic vgap at each side of said coilbobbin.

References Cited by the Examiner OTHER REFERENCES Radio-Electronics,August 1960, page 43.

Mann: The Month in Science, Popular Science, December 1960, pages 29 and30.

HERMAN KARL SAALBACH, Primary Examiner. ARTHUR GAUSS, Examiner.

D. D, FORRER, C. BARAFF, Assistant Examiners.

3. A POLE PIECE STRUCTURE, TWO OF WHICH USED TOGETHER PROVIDE A PAIR OFALIGNED SPACED APART MAGNETIC GAPS HAVING SUBSTANTIALLY IDENTICALCHARACTERISTICS, COMPRISING A NARROW RECTANGULAR SHEET METAL STRIPADAPTED TO EXTEND INTO A CORE PASSAGE OF A COIL, SAID CORE STRIP HAVINGAN INTEGRAL TAB AT ONE END EXTENDING AT RIGHT ANGLES TO THE PLANE OF THECORE STRIP, SAID TAB BEING INTEGRALLY EDGE JOINED TO AN OFFSETTRANSVERSELY EXTENDING STRIP HAVING OFF-